HP Modular Cooling System - Manual (Page 63)

Water quality and leveling requirements, and condensation management 63
Water quality and leveling requirements, and
condensation management
Water quality requirements and specifications
Closed-loop water must not contain any lime scale deposits or loose debris. The water must have a low level
of hardness, particularly a low level of carbon hardness. Filters must be used to remove free floating
particulates and be regularly maintained. Additionally, the water must not be so soft that it attacks the
materials with which it comes into contact. You must periodically add new fresh water, but also to remove
some enriched water. HP recommends a #30 mesh filter is recommended for filtering water entering the MCS
5042 unit and a 1 µm filter for prolonged performance.
Also consider the required set point for the water temperature. Temperatures near or below 0ºC (32ºF) mean
that the chilled water plant condenser is very close to or below the freezing point of the water. The chilled
water temperature to be supplied to the MCS 5042 unit is 5ºC (41ºF). Freezing water can cause a blockage
and damage to the unit. Therefore, an additive such as glycol might be necessary to lower the freezing point.
However, the heat transfer potential of the water is lower, so the equipment must be derated properly.
In a cooling loop, metallic materials in a pipe distribution network are in constant contact with recirculating
liquid and can react with impurities to cause corrosion that can develop into leaks or form deposits and
blockages.
The rate of galvanic corrosion depends on the electrical potential between the two dissimilar metals and the
temperature of the liquid.
A 10-degree increase in water temperature can double the rate of corrosion.
For more information, see the HP mc-Series 5042 Rack Site Preparation Guide on the HP website
(
http://www.hp.com ).
Acceptable water quality specifications
The following values are water quality ranges required for continuous quality of performance.
Parameter Range
pH
8.0–10
Specific conductance at 25ºC (77ºF) 10–2500 µmhos
Alkalinity ("M" as CaCO
3)
150–1000 ppm
Sulfur (SO
4
) 0–150 ppm
Chloride (Cl)
0–100 ppm
Hardness (CaCO
3
) 0–350 ppm
Calcium hardness (CaCO
3
) 0–200 ppm
Magnesium hardness (CaCO
3
) 0–150 ppm
Copper (Cu)
< 0.20 ppm
Iron (Fe) < 3.0 ppm
Aluminum (Al) < 0.50 ppm